The use of implants to affix tissue grafts to bone is well known in the orthopedic arts. Common procedures in which such implants are used include, for example, the repair of rotator cuff tears, the repair of torn ligaments in the knee, among others. In these procedures, a socket is drilled or punched in the bone at the attachment site and a graft is secured to the bone using an implant placed in the socket. The graft may be secured to the implant by sutures, or, alternatively, an end of the graft may be placed in the socket and secured directly by an implant.
In rotator cuff repair implants commonly referred to as “anchors” are used. These anchors occur in two types: conventional anchors, in which the suture is passed through the cuff after anchor placement, and “knotless” anchors, in which the suture is passed through the cuff prior to anchor placement. In the former case, the graft is secured in place by tying knots in the suture after it has been passed through the cuff so as to secure the cuff in the desired location. Conversely, as the name implies, when using a knotless anchor, the sutures are passed through the cuff and through a locking feature of the anchor such that when the anchor is inserted into the socket, the suture position is secured by the anchor. The tying of knots is not required. This is particularly advantageous when performing endoscopic (arthroscopic) repairs since the tying of knots arthroscopically through a small diameter cannula may be difficult for some surgeons and, moreover, there is an opportunity for tangling of the sutures.
Knotless suture anchor fixation is a common way of repairing soft tissue that has been torn from bone. The procedure requires drilling or punching of holes into a properly prepared boney surface. After suture has been passed through soft tissue the suture anchor is introduced into the socket and driven into the socket using a mallet or by screwing the anchor into the socket using a driver device. These driver devices typically resemble a screwdriver in form, having a proximal handle portion for applying torque or percussive force, and an elongate rigid distal portion having at its distal end a torque or percussive force-transmitting configuration. In the case of torque transmitting drivers used with threaded anchors, the distal end of the driver typically has an elongate hexagonal or square distally extending portion that, through coupling with a lumen in the anchor having a complementary cross-section, transmits torque to the anchor. The lumen may extend through anchor so that the distal portion of the driver protrudes from the distal end of the anchor and rotates with the anchor during anchor placement. Illustrative examples of such “knotless” anchors include the SwiveLock® Knotless Anchor system by Arthrex, Incorporated (Naples, Fla.), the HEALIX Knotless™ Anchor by Depuy/Mitek, Incorporated (Raynham, Mass.), and the Knotless Push-In Anchors such as the Knotless PEEK CF Anchor by Parcus Medical (Sarasota, Fla.)). These anchors and their associated repair techniques have certain drawbacks, primarily stemming from difficulties in maintaining suture separation and preventing rotation of sutures during anchor placement. For example, in the case of the SwiveLock®, the suture is placed at the bottom of the socket via a PEEK (PolyEther Ether Ketone) eyelet that remains at the bottom of the hole. This eyelet can fracture at insertion resulting in a loss of rotational control of the sutures which, in turn, results in suture spin and variation in the tension as well as possible loss of fixation of the suture tension and loss of the suture from the eyelet, all of which add up to failure of the anchor. In the case of the HEALIX Knotless™ anchors, the sutures pass directly through the body of the anchor and, upon insertion of the anchor, the sutures spin around the anchor, thereby resulting in incomplete tension on the sutures as well as change in the suture tension—both of which can result in movement of the tissue through which the suture was placed.
In U.S. Pat. No. 6,544,281, ElAttrache et al. describe a cannulated driver having a rotating inner member and a stationary outer member, wherein the rotating inner member serves to drive the threaded anchor. The rotating member extends past the distal end of the anchor and is inserted into a prepared socket in the boney surface. Sutures attached to the graft, i.e., captured sutures, are used to draw the graft to the desired position prior to placement of the anchor. However, because the sutures are captured to or pass through the rotating inner member, the sutures are twisted during anchor insertion thereby changing the tension on the sutures and the graft position.
Other knotless anchors such as the ReelX STT™ Knotless Anchor System by Stryker® Corporation (Kalamazoo, Mich.) and PopLok® Knotless Anchors by ConMed Corporation (Utica, N.Y.) have complex constructions and require that the surgeon perform a sequence of steps to achieve a successful anchor placement with the desired suture tension and proper cuff position. The sequence of steps adds to procedure time and creates opportunities for failure of the placement procedure if a step is not performed properly.
Accordingly, there is a need in the art for a knotless anchor system that allows the surgeon to establish the graft position and, while maintaining that position, place the anchor without changing the suture tension or causing a shift in the graft position. Furthermore, if the anchor is threaded, placement of the anchor in the socket must occur without spinning of the suture.
If a graft is directly affixed to a bone by insertion of a graft into a socket (a technique referred to as “bio-tenodesis”), it is essential that the graft be fully inserted so as to engage with the full length of the implant. It is also important that the position of the graft be maintained during anchor insertion. Further, it is essential that the alignment of the implant (in this case referred to as an “interference screw”) be coaxial, or if slightly shifted, parallel to the axis of the socket. It is also desirable for the sutures used to draw the graft into the socket not to spin or twist during anchor placement as this may change the position and tension of the graft from that intended by the surgeon. In sum, there is also a need in the suture arts for an interference screw and implant placement system in which graft position within the socket is maintained throughout the implant placement process, and in which suture spin or twisting is prevented.
Current placement systems for threaded implants use a driver that is rigidly coaxial throughout its proximal and distal portions and is coaxial with the implant. Of necessity, the implant is placed coaxially within the prepared socket. Because the sockets are formed using a punch or drill, an item that is itself rigidly coaxial throughout, placement of anchors in sockets so produced are not limited by the rigid coaxial nature of the implant driver devices. This limits the locations in which anchors and interference screws may be placed, particularly when procedures are performed arthroscopically. However, in U.S. Provisional Application Ser. No. 61/965,973 filed Feb. 13, 2014, the contents of which are herein included by reference in its entirety, the present inventors describe a drilling device in which the distal portion may be angularly offset by the surgeon so as to produce holes having an axis offset from that of the more proximal portions of the drilling device. Using devices so configured, it is possible to produce sockets for anchors in locations that cannot be accessed by drills or anchor driver systems in which the distal portion is not angularly offset. Accordingly, there is further a need in the suture arts for anchor systems, both conventional and knotless, and for interference screw placement systems in which anchors may be placed in sockets the axis of which is not coaxial with the driving assembly axis. That is, in which the anchor and the distal portion of the driving assembly are coaxial with the socket, but the other portions of the driver assembly are not. Further, since some implants require that threads be formed in the socket prior to placement of a threaded implant, there is a need in the art for a thread-forming device in which the axis of the rotating thread-forming portion is not coaxial with the proximal portions of the torque producing member. The availability of such “off-axis” drills and implant systems such as contemplated herein will greatly simplify commonly performed procedures, such as Anterior Cruciate Ligament (ACL) repair, since current methods are limited to constructs that can be produced by conventional coaxial drills and interference screw placement systems.